Q6: Design WhatsApp

       Real-time messaging via WebSockets, message queues, encryption, and offline delivery
       Use distributed databases.

Q7: Design a Notification System
       Use push/polling mechanisms, message queues, retry logic, and user preferences.

Q8: Design a File Storage System
      Use chunking, metadata indexing, replication, and deduplication
      Consider S3-like architecture.

Q9: Design Google Docs
       Real-time collaboration via operational transformation or CRDTs
       Use WebSockets and versioning.

Q10: Design a Video Streaming Service
         Use adaptive bitrate streaming, CDN, encoding pipelines, and metadata indexing.

Q11: Design a Ride-Sharing App
        Match riders and drivers using geolocation, ETA algorithms, surge pricing, and real-time updates.

Q12: Design a News Feed
         Use ranking algorithms, caching, pagination, and user personalization.

Q13: Design a Search Engine
         Use crawling, indexing, ranking algorithms, and distributed storage.

Q14: Design a Payment Gateway
         Ensure security, transaction logs, fraud detection, and integration with banks.

Q15: Design a Booking System
         Handle availability, concurrency, calendar views, and notifications.

Q16: Design a Chat Application
         Use WebSockets, message queues, encryption, and delivery receipts.

Q17: Design a Job Scheduler
         Use priority queues, worker threads, retry logic, and logging.

Q18: Design a CDN
         Use edge servers, caching strategies, and load balancing.

Q19: Design a Logging System
         Use log aggregation, indexing, search, and alerting.

Q20: Design a Metrics Dashboard

         Use time-series databases, visualization tools, and alerting.

Q21: Design a Document Collaboration Tool
         Use real-time sync, version control, and conflict resolution.

Q22: Design a Polling System
         Handle vote counting, concurrency, and result aggregation.

Q23: Design a Leaderboard
         Use sorted sets, caching, and real-time updates.

Q24: Design a Recommendation System
         Use collaborative filtering, content-based filtering, and ranking.

Q25: Design a Social Network
         Handle user profiles, connections, feeds, and privacy settings.

Q26: Design a Multi-Tenant SaaS App
         Use tenant isolation, shared resources, and scalability.

Q27: Design a Real-Time Analytics System
         Use stream processing, windowing, and dashboards.

Q28: Design a Distributed Locking System
         Use Redis or Zookeeper for lock coordination and expiration.

Q29: Design a Feature Flag System
         Use toggles, rollout strategies, and audit logs.

Q30: Design a Version Control System
         Use DAGs, branching, merging, and conflict resolution.

Q31: Design a Survey Platform
         Handle question types, responses, analytics, and exports.

Q32: Design a Task Management App
         Use boards, lists, notifications, and user roles.

Q33: Design a Content Moderation System
         Use ML models, queues, human review, and audit trails.

Q34: Design a Fraud Detection System
         Use anomaly detection, rule engines, and alerts.

Q35: Design a Cloud Storage System
         Use replication, encryption, access control, and billing.

Q36: Design a Load Balancer
         Use round-robin, least connections, and health checks.

Q37: Design a Queue System
         Use FIFO/LIFO, retries, dead-letter queues, and monitoring.

Q38: Design a Video Conferencing App
         Use media servers, signaling, STUN/TURN, and recording.

Q39: Design a Document Indexing System
         Use inverted indexes, tokenization, and ranking.

Q40: Design a Real-Time Bidding System
         Use auctions, latency optimization, and fraud prevention.

Q41: Design a Shopping Cart System
         Handle sessions, inventory, pricing, and checkout.

Q42: Design a Loyalty Program
        Track points, tiers, rewards, and redemption.

Q43: Design a Multi-Region Deployment
         Use replication, failover, latency optimization, and DNS routing.

Q44: Design a Data Pipeline
          Use ETL, batch/stream processing, and monitoring.

Q45: Design a Schema Registry
          Use versioning, compatibility checks, and metadata.

Q46: Design a Mobile Backend
         Use APIs, push notifications, and offline sync.

Q47: Design a Health Monitoring System
         Use sensors, alerts, dashboards, and data storage.

Q48: Design a Quiz Platform
         Handle question banks, scoring, timing, and analytics.

Q49: Design a Code Execution Engine
         Use sandboxing, resource limits, and language support.

Q50: Design a Resume Parser
         Use NLP, templates, and structured output.